(a) Field of the Invention
The present invention relates to an apparatus for calibrating amplitude and phase errors, a multiport amplifier including the same, and a method of amplifying the multiport amplifier. More particularly, the present invention relates to a method and apparatus for simultaneously detecting and calibrating phase and magnitude errors in a multiport amplifier.
(b) Description of the Related Art
A multiple beam antenna system that can provide narrow beams having a high antenna gain within a service coverage area is widely used as a mounting body system of a communication and broadcasting satellite due to excellent equivalent isotropically radiated power (EIRP) and G/T performance, which is a ratio of a gain G of an antenna and a noise temperature T.
In the multiple beam antenna system, a multiport amplifier that can perform output power control according to an operation condition is widely used.
The multiple beam antenna system using a multiport amplifier installs several spot beams within a service area to provide communication and broadcasting services and flexibly provides high power allocation to an area requiring higher EIRP due to rainfall or a rapid increase of a communication service. Further, because the multiport amplifier combines and uses high power amplifiers having the highest failure rate in parallel among components for a satellite repeater, when using the multiport amplifier, a system can be formed using a high power amplifier redundancy of a fewer number, compared with when using an existing satellite repeater.
The multiport amplifier has a plurality of input terminals and output terminals and the number of input terminals and output terminals may be 2n, but in consideration of ease of embodiment or optimal performance, the most available structures are a 4×4 structure and an 8×8 structure.
The multiport amplifier generally operates using hybrid matrix characteristics, and an operation principle of such a multiport amplifier is achieved when connection components such as input and output hybrid networks, a power amplifier, and other transmission lines perform an ideal operation.
Actually, when embodying a multiport amplifier, a hybrid matrix has a difference in insertion loss of terminals and has an error in phases. In a power amplifier, by nonlinearity, a phase of an output signal has different values according to the magnitude of an input signal. When connection components such as a transmission line are not manufactured in the same size and form, the amplitude (magnitude) and phase of a signal may be changed. In this way, in components constituting a multiport amplifier, when an error occurs in an amplitude and a phase, as in an ideal operation, an in-phase or out-of-phase condition of signals that are distributed in input and output hybrid networks is not achieved and thus isolation performance between input terminals and output terminals of the multiport amplifier is deteriorated.
In order to solve such a problem, the multiport amplifier includes a signal magnitude and phase calibration circuit. In order to prevent power loss of an output terminal, the magnitude and phase calibration circuit is disposed at a front stage of the power amplifier, and in an output hybrid network, the multiport amplifier maintains magnitude and phase differences of a signal, as in a ideal multiport amplifier, thereby performing a function of improving isolation performance of the multiport amplifier. In the phase and magnitude calibration circuit, values of a phase and a magnitude are determined as values that can embody optimum performance while including actual performance of each component when embodying a multiport amplifier system. However, when a change occurs in the performance of constituent elements of a multiport amplifier by an environment condition change such as degradation of a component performance or a temperature change, the performance of the multiport amplifier cannot be maintained in an optimal state.